[Issue #20] Adding #ifdef to use class_getClassMethod for allowsReverseTransformation on iOS <= 5
[Issue #20] Adding #ifdef to use class_getClassMethod for allowsReverseTransformation on iOS <= 5

gaurav1981/TransformerKit,gaurav1981/TransformerKit,zhaoguohui/TransformerKit,mattt/TransformerKit,zhaoguohui/TransformerKit,kgn/TransformerKit,mattt/TransformerKit,mattt/TransformerKit